(1) Field of the Invention
The present disclosure relates to a sheet-shaped fiber structure made of fibrous silicon dioxide. The present disclosure also relates to a filter device as a part of a microreactor, a chemical chip, a biochip, a lab-on-a-chip, a nanochip, a chromatograph, or the like, which includes a sheet-shaped fiber structure for use in extracting only a specific material from a solution, and also relates to an analysis device using such a filter device.
(2) Description of Related Art
A filter device, as an example of application using a sheet-shaped fiber structure, aims to separate only a specific material (object to be examined) from a sample containing a plurality of materials, and is needed in a variety of fields.
For example, the surface of a first substrate made of quartz is subjected to a chemical treatment such as dry etching or wet etching, or a processing using a laser beam, an ion beam or energy ray irradiation to form a plurality of island-shaped columns. Subsequently, a second substrate made of silicon is bonded to the first substrate in such a manner that the columns are sealed between the substrates. The interstices between the island-shaped columns sealed between the first and second substrates are used as filter flow paths, as shown in Japanese Patent Laid-Open Publication No. 2002-239317.
Also disclosed is a device including a first substrate and a flow path groove formed on the surface of the first substrate, as shown in International Patent Publication No. WO 2010/082279. According to the device, a fibrous layer including a plurality of fibrous projections is provided in the flow path groove and located to its opening.
Also disclosed is a material for removing leukocytes, which contains 0.5% by weight or more and less than 50% by weight of ultra fine fibers each having a diameter of 0.02 μm or more and less than 0.8 μm, as shown in Japanese Patent Laid-Open Publication No. 11-12181. According to the material, the ultra fine fibers form a network structure having a circularity of 1.7 or less and an equivalent circle diameter of 1 μm or more and less than 20 μm.
Also disclosed is a member for removing leukocytes, which contains 5% by weight or more and less than 20% by weight of ultra fine fibers each having a diameter of 0.1 μm or more and less than 0.6 μm, as shown in Japanese Patent Laid-Open Publication No. 11-12180. According to the member, the ultra fine fibers have a degree of curvature of 1.2 or more
An analysis chip, as an example of application using a filter device, conventionally has purposes such as purifying or isolating a very small amount of a product and analyzing components, and generally includes a column tube and a silica gel which is a column filler packed as a solid phase in the column. A known method for producing the silica gel is a method for producing a porous inorganic material by a sol-gel reaction using, as a raw material, an oxide material containing an organic compound such as an alkoxide. Specifically, the silica gel is produced as follows. A silica sol is formed by hydrolyzing, in the presence of an acid, an alkoxysilane in water or a mixed solution of water and an alcohol. The resulting silica sol is added to an oil-based dispersion medium including an aromatic hydrocarbon such as benzene, toluene, xylene, or ethylbenzene and an emulsifier such as a long-chain organic carboxylic acid or a surfactant. The mixture is stirred using a mixer such as a homomixer, and the resulting emulsion is formed into a gel. This production method is one of the most easily practicable methods and thus performed preferably. The silica gel produced by this method is used as a high-performance liquid chromatography filler because it has distinctive surface physical properties, as shown in International Patent Publication No. WO 2006/001300.